/* PBKDF2.java -- 
   Copyright (C) 2003, 2006 Free Software Foundation, Inc.

This file is a part of GNU Classpath.

GNU Classpath is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
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WITHOUT ANY WARRANTY; without even the implied warranty of
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General Public License for more details.

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USA

Linking this library statically or dynamically with other modules is
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permission to link this library with independent modules to produce an
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package gnu.javax.crypto.prng;

import gnu.java.security.prng.BasePRNG;
import gnu.java.security.prng.LimitReachedException;
import gnu.javax.crypto.mac.HMac;
import gnu.javax.crypto.mac.IMac;

import java.io.UnsupportedEncodingException;
import java.util.Arrays;
import java.util.HashMap;
import java.util.Map;

/**
 * An implementation of the <i>key derivation function</i> KDF2 from PKCS #5:
 * Password-Based Cryptography (<b>PBE</b>). This KDF is essentially a way to
 * transform a password and a salt into a stream of random bytes, which may then
 * be used to initialize a cipher or a MAC.
 * <p>
 * This version uses a MAC as its pseudo-random function, and the password is
 * used as the key.
 * <p>
 * References:
 * <ol>
 * <li>B. Kaliski, <a href="http://www.ietf.org/rfc/rfc2898.txt">RFC 2898:
 * Password-Based Cryptography Specification, Version 2.0</a></li>
 * </ol>
 */
public class PBKDF2
    extends BasePRNG
    implements Cloneable
{
  /**
   * The bytes fed into the MAC. This is initially the concatenation of the salt
   * and the block number.
   */
  private byte[] in;
  /** The iteration count. */
  private int iterationCount;
  /** The salt. */
  private byte[] salt;
  /** The MAC (the pseudo-random function we use). */
  private IMac mac;
  /** The number of hLen-sized blocks generated. */
  private long count;

  /**
   * Creates a new PBKDF2 object. The argument is the MAC that will serve as the
   * pseudo-random function. The MAC does not need to be initialized.
   * 
   * @param mac The pseudo-random function.
   */
  public PBKDF2(IMac mac)
  {
    super("PBKDF2-" + mac.name());
    this.mac = mac;
    iterationCount = -1;
  }

  public void setup(Map attributes)
  {
    Map macAttrib = new HashMap();
    macAttrib.put(HMac.USE_WITH_PKCS5_V2, Boolean.TRUE);
    byte[] s = (byte[]) attributes.get(IPBE.SALT);
    if (s == null)
      {
        if (salt == null)
          throw new IllegalArgumentException("no salt specified");
        // Otherwise re-use.
      }
    else
      salt = s;
    byte[] macKeyMaterial;
    char[] password = (char[]) attributes.get(IPBE.PASSWORD);
    if (password != null)
      {
        String encoding = (String) attributes.get(IPBE.PASSWORD_ENCODING);
        if (encoding == null || encoding.trim().length() == 0)
          encoding = IPBE.DEFAULT_PASSWORD_ENCODING;
        else
          encoding = encoding.trim();
        try
          {
            macKeyMaterial = new String(password).getBytes(encoding);
          }
        catch (UnsupportedEncodingException uee)
          {
            throw new IllegalArgumentException("Unknown or unsupported encoding: "
                                               + encoding, uee);
          }
      }
    else
      macKeyMaterial = (byte[]) attributes.get(IMac.MAC_KEY_MATERIAL);

    if (macKeyMaterial != null)
      macAttrib.put(IMac.MAC_KEY_MATERIAL, macKeyMaterial);
    else if (! initialised)
      throw new IllegalArgumentException(
          "Neither password nor key-material were specified");
    // otherwise re-use previous password/key-material
    try
      {
        mac.init(macAttrib);
      }
    catch (Exception x)
      {
        throw new IllegalArgumentException(x.getMessage());
      }
    Integer ic = (Integer) attributes.get(IPBE.ITERATION_COUNT);
    if (ic != null)
      iterationCount = ic.intValue();
    if (iterationCount <= 0)
      throw new IllegalArgumentException("bad iteration count");
    count = 0L;
    buffer = new byte[mac.macSize()];
    try
      {
        fillBlock();
      }
    catch (LimitReachedException x)
      {
        throw new Error(x.getMessage());
      }
  }

  public void fillBlock() throws LimitReachedException
  {
    if (++count > ((1L << 32) - 1))
      throw new LimitReachedException();
    Arrays.fill(buffer, (byte) 0x00);
    int limit = salt.length;
    in = new byte[limit + 4];
    System.arraycopy(salt, 0, in, 0, salt.length);
    in[limit++] = (byte)(count >>> 24);
    in[limit++] = (byte)(count >>> 16);
    in[limit++] = (byte)(count >>> 8);
    in[limit  ] = (byte) count;
    for (int i = 0; i < iterationCount; i++)
      {
        mac.reset();
        mac.update(in, 0, in.length);
        in = mac.digest();
        for (int j = 0; j < buffer.length; j++)
          buffer[j] ^= in[j];
      }
  }
}